1. Technical Field
The present invention relates to a wireless communication system, and more specifically, to a carrier aggregation technology for small base stations.
2. Discussion of Related Art
A home base station is installed in a small cell environment such as a building or home, and may be purchased, installed, and operated by a user. Accordingly, a number of home base stations may be installed and used in a macro base station regardless of a service provider's plan. This may cause a serious interference concern.
According to the current 3GPP standards, a CSG HeNB (Home evolved NodeB) or a hybrid HeNB having a CSG (Closed Subscriber Group) ID continues to broadcast its CSG indication information and CSG ID through system broadcast information. One CSG HeNB or hybrid HeNB is restricted as having one CSI ID.
In the case of CSG HeNBs, user terminal (UE) having a CSG function may gain access to a corresponding CSG HeNB only upon entry into a CSG HeNB cell region to which the UE subscribes. In contrast, when entering into a CSG HeNB cell region to which the UE does not subscribe, the UE cannot gain access to the CSG HeNB.
The information on the CSG to which the UE subscribes is stored in the SIM (Subscriber Identity Module) card of the UE in the form of a CSG white list. That is, for a service, the CSG ID number of the CSG HeNB is included in the CSG white list of the UE.
Meanwhile, in the case of hybrid HeNBs, when UE having a CSG function enters into a hybrid HeNB cell region to which the UE subscribes, the UE may access the hybrid HeNB and may have a priority in assignment of wired/wireless resources. On the contrary, when attempting to enter into an unsubscribed hybrid HeNB cell region, the UE may gain access thereto depending on availability of wired/wireless resources of the hybrid HeNB, but cannot have a priority for the wired/wireless resources.
Accordingly, in case the wired/wireless resources of the hybrid HeNB are insufficient, the UE might not access the hybrid HeNB, or even succeeding in the access, the UE may be kicked out while on service.
Further, the information on the CSG to which the UE subscribes is stored in the SIM card of the UE in the form of a CSG white list, so that the CSG ID number of the hybrid HeNB is included in the CSG white list for a service.
A plurality of component carriers may be aggregated and used. At this time, a circumstance may occur where a macro eNB and a home eNB co-exist, i.e., a situation where a macro eNB and a CSG home eNB share the same frequency.
A need exist for a method or apparatus of controlling interference that may be caused when the same frequency is shared in such carrier aggregation circumstance.